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Diagnostics JSON output

Error codes M0000 error M0001 syntax error M0002 undefined name M0003 no such field or method M0004 declared and not used M0005 imported and not used M0006 type mismatch M0007 mismatched types M0008 wrong number of return values M0009 wrong number of arguments M0010 missing return M0011 package not found M0012 assignment count mismatch M0013 no new variables M0014 does not implement interface M0015 redeclared M0016 invalid operation M0017 bad command line M0018 link error M0019 internal compiler error M0020 runtime panic M0021 fatal runtime error M0022 test failed M0023 import cycle M0024 name not exported M0025 not supported by marmot M0026 type argument does not satisfy constraint M0027 cannot infer type argument M0028 shadowed variable M0029 unknown struct field M0100 vet finding M0101 lint finding M0102 modernize suggestion M0103 not formatted M0104 gopls finding M0105 known vulnerability M0106 go.mod not tidy M0107 cross build failure M0108 unreachable function M0109 switch misses cases M0110 possible nil dereference M0111 heap allocation

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DiagnosticsError codes

M0103 not formatted

The file is not in gofmt layout, or its imports are not as goimports would write them.

Last updated Nov 13, 2026View as Markdown Agent setup

The fix

Run marmot fmt.

See also all error codes and marmot explain.

M0102 modernize suggestion

The code can use a newer language or library feature that the module's go version allows (min and max, range over int, slices and maps functions, strings.Cut, ...).

M0104 gopls finding

An analyzer of gopls (simplifications, unused parameters, ...) has a suggestion.

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